Wind force field only works in the center of the scene
The Wind force field gives a constant force in a single direction. It's like a Sun light but emitting force instead of light, so You can imagine it as an endless flat plane emitting force.It's a global force. You can change only direction of it.
I checked your file and everything seams to be ok. It worked wherever I put cloth or wind source, so when You noticed it's not working You must've not back the animation to start position.